The present invention relates generally to underwater electrical and/or fiber-optic cable systems, such as underwater telecommunication systems, and is particularly concerned with an apparatus and method for providing branching and re-distribution of circuits in such a system after installation.
Currently, it is very difficult to re-connect or re-distribute circuits when an electrical/optical cable system has been previously submerged deep underwater, such as on the ocean floor. The present technology involves grappling and retrieval of cables from the ocean floor, such that they often have to be drawn up from several miles of ocean depth, and subsequently separated and re-terminated via splicing on board a cable laying ship, using ship-board facilities. This procedure is extremely laborious, time-consuming and expensive. Also, such procedures are very vulnerable to weather and ocean conditions, since storms or other inclement weather conditions can severely limit or jeopardize the successful completion of such operations.
It is an object of the present invention to provide a new and improved self-contained cable branching apparatus and method for ocean floor installation.
According to one aspect of the present invention, an ocean floor cable branching apparatus is provided, which comprises a cable junction housing for positioning in-line between two main cables for installation underwater, the housing having a first junction at one end having a through bore for receiving the end of a first cable and a second junction at the opposite end having a through bore for receiving the end of a second cable, a circuit distribution unit inside the housing having a first port connected to the end of the first cable, a second port connected to the end of the second cable, and at least two additional, third and fourth ports, a switch assembly in the circuit distribution unit for selectively connecting the first port to the second port in a straight through arrangement, and connecting the first and second ports to the third and fourth ports, respectively, at least two wet mateable underwater connectors in the housing each comprising a plug unit and a socket unit releasably connected with the plug unit, one of the units comprising a dummy unit and the other unit being connected to a respective one of the third and fourth ports, and a connector mounting mechanism in the housing for movably mounting the respective plug and socket units for movement between an inactive, stowed condition in which each plug unit is aligned with and connected to the respective socket unit, and a released, deployed condition in which the plug and socket units are separated, the dummy unit is discarded, and the remaining unit is deployed for selective connection to a mating unit at the end of a branch cable to be connected to one of the main cable ends.
In an exemplary embodiment of the invention, there are four additional ports and four underwater connectors, each with an active unit connected to a respective one of the additional ports. Some or all of the connectors may be disconnected, with the dummy unit discarded and the active unit connected to a respective branch cable, and the circuit distribution unit appropriately switched to connect each branch cable to respective circuits in a selected main cable, providing a selected circuit configuration. In an even more versatile arrangement, two identical housings are connected in line in a tandem arrangement, with each housing containing a circuit distribution unit and associated underwater connectors.
In an exemplary embodiment of the tandem arrangement, each housing has a spherical or ball joint arrangement at each end, with a central, double ball joint between the two housings, providing a wide range of articulation. Each housing may be capable of articulating to 90 spherical degrees or more. The entire assembly is designed to be axially mounted into a length of oceanic cable, and to be deployable over a standard cable-laying sheave, making installation easy and inexpensive.
The or each housing has at least one opening for access to the connectors, and one or more doors for normally closing the opening, which can be opened by a remote oceanic vehicle (ROV) when the cable ends are to be re-connected to branch cables. The ROV can manipulate the connector mounting mechanism in order to disconnect the connector units, discard or retrieve the dummy units, and connect the port connector units to one or more branch cables. Additionally, the ROV can be controlled to adjust the circuit handling unit to accommodate the new circuit configuration. The connectors may be wet mateable underwater optical or electro-optical connectors which are designed for sealed, releasable underwater connection of electrical and/or optical fiber circuits in underwater cables. Suitable wet mateable connectors are described, for example, in U.S. Pat. Nos. 5,738,535 or 6,017,227 of Cairns, or pending U.S. patent application Ser. No. 09/641,313 of Barlow et al., Ser. No. 09/418,145 of Cairns filed Oct. 14, 1999 or Ser. No. 09/761,917 of Cairns et al. filed Jan. 17, 2001.
According to another aspect of the present invention, a method of releasably connecting the ends of two cables in-line and subsequently separating the cable ends and joining them to branch cables is provided, which comprises the steps of:
securing an end of a first cable to a first port of a circuit distribution unit mounted inside a housing;
securing an end of a second cable to a second port of the circuit distribution unit with the circuit distribution unit arranged to connect the first port to the second port;
securing first and second underwater connectors to third and fourth ports of the circuit distribution unit inside the housing, with each connector comprising an active connector unit connected to the respective port and a dummy unit releasably connected to the active connector unit;
deploying the cables and housing underwater as part of a sub-oceanic cable communication network;
at a subsequent date, disconnecting at least one dummy unit from the corresponding active unit, and connecting the active unit to a mating connector of a branch cable; and
adjusting the circuit distribution unit to connect the branch cable to one of the in-line cables.
In an exemplary embodiment, both of the dummy units are disconnected from the respective port connector units and discarded, and separate branch cables are connected to the respective port connector units, with the circuit distribution unit being adjusted to connect one of the branch cables to one of the in-line cables, and the other branch cable to the other in-line cable.
The method and apparatus of this invention allows installation of branching devices along each line when laying a new, sub-oceanic cable network for telecommunications or the like. Subsequent branching and re-circuiting can then be readily performed by an ROV on the ocean floor at any desired branching apparatus location. Further revisions can be made at a later date, whenever required, substantially increasing the flexibility and modification capabilities of such systems. The performance of modifications and additions on the ocean floor by an ROV will significantly reduce the hazards to both equipment and personnel, by avoiding the need to raise a previously laid cable through possibly miles of ocean depth onto a cable laying ship, and then separate and re-splice the cable on board the ship. Branching and re-circuiting operations, as well as initial installation, will be less vulnerable to adverse weather conditions which can otherwise cause substantial, and expensive, delays in such operations.